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DP83869HM: Placing part in BIST mode with digital loopback not seeing Link-Up

jason gutel
Prodigy 20 points

Part Number: DP83869HM

Tool/software:

Following the instructions in the Reference Manual Section 7.3.5 BIST Configuration to place the part in digital loopback mode and then checking the link status register (0x1) we are not seeing the Link Up like the manual suggests it should be.

Performing the following,
1. Write 0xe720 to register 0x00fe
2. Write 0x0140 to register 0x0
3. Write 0x5028 to register 0x10
4. Write 0x4 to register 0x16
5. Read register 0x1 -> Get back 0x7949 indicating the link is down

The reference manual states "the PHY link status will go high, regardless if there is a cable connected or not".

Any suggestions on how to further debug this? The device is boot-strapped to be in RGMII-to-SGMII mode and the steps above were performed after a initial hardware reset of the PHY.

  • +1
    TI__Mastermind 37925 points

    Hi Jason,

    If you're in RGMII to SGMII mode the copper link status would not be used. Its likely this bit is not updated when the PHY is not configured for a mode that uses the copper link. The BIST configuration example in section 7.3.5 assumes the copper interface is used. This example outputs a PRBS pattern on the copper MDI:

    Are you only trying to perform a digital loopback test or do you need to generate a PRBS signal?

    Best,

    Shane

  • 0 in reply to Shane Hauser
    TI__Mastermind 37925 points

    Hi Jason,

    Checking in on this thread. Did you have any more questions on this device?

    If not, I'll go ahead and mark this as resolved.

    Best,

    Shane